Process piping velocity erosion

Water containing 0.01 wt% sand is flowing through a pipe at a flow velocity of 60 m/s. Describe how the annual erosion depth increment in the pipe wall can be calculated on the basis of short duration tests in a similar pipe where the sand concentration in the water is varied in the range 0.1-10 wt% and the flow velocity in the range 20—40 m/s. Assume in the first instance that the deterioration process is mainly erosion and only little corrosion. 

Velocities. Revamp process piping so that velocities are less than 10 ft/sec. For exchangers, hold velocities below 3 fl/sec. Remember, rapidly flowing amine is erosive. 

High-fluid velocity will tend to erode off the protective corrosion layer inside process piping. This exposes new, clean, and reactive metal to the corrosive oxygen and water. What is meant by erosive velocity For aqueous systems with a few hundred parts per million (ppm) of particulates, an erosive velocity is... 

Pressures, temperatures, suspended solids, and their solubilities (and erosive properties) since deposition of some solids inside can reduce life of pipes. Details of feeding system for materials into process reactors and vessels. Diameters of all pipes (and velocities of flowing fluids insides), materials of construction, and their routes. 

Erosion corrosion is associated with a flow-induced mechanical removal of the protective surface film that results in subsequent corrosion rate increases via either electrochemical or chemical processes. It is often accepted that a critical fluid velocity must be exceeded for a given material. The mechanical damage by the impacting fluid imposes disruptive shear stresses or pressure variations on the material surface and/or the protective surface film. Erosion corrosion may be enhanced by particles (solids or gas bubbles) and impacted by multi-phase flows [29]. Increased flow stream velocities and increases of particle size, sharpness, density, and concentration increase the erosion corrosion rate. Increases in fluid viscosity, density, target material hardness, and/or pipe diameter tend to decrease the corrosion rate. The morphology of surfaces affected by erosion corrosion may be in the form of shallow pits or horseshoes or other local phenomena related to the flow direction. 

Formula (VI.33) is valid for the removal of a layer of sand and coal 0.5-1 mm thick with particle dimensions of 15-90 m in pipes 100-400 mm in diameter. The air velocity necessary to overcome the forces of autohesion in the erosion process may be calculated from this formula. For complete removal of the adhering particles, i.e, in order to overcome the adhesive force of the dust layer to the inner surface of the pipeline, the air velocity must be considerably higher than the value calculated from formula (VI.33). On increasing the air-flow velocity it is possible to overcome the adhesive forces of the remaining particles and clean the surface from the adhering dust layer. Hence, for Fad > F, we must distinguish two air-flow velocities. The first characterizes the conditions under which the forces of autohesion are overcome, while the second relates to adhesive forces. The first of these velocities is always smaller than the second. ... 

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